Heat transfer support surfaces with multiple heat transfer elements in parallel that use orifices to control the fluid flow are disclosed in U.S. Pat. No.'s 5,086,693, 5,960,869, and 6,263,963 to Tippmann et al, all incorporated by reference.
In general, the support surface includes multiple heat transfer elements positioned in parallel. Each heat transfer element contains at least one passageway for transferring heat to or from the fluid circulating therein. Headers are used to interconnect the fluid flow at both ends of the heat transfer elements.
In order for the support surface to transfer the amount of heat required, the fluid contact surface area of the internal passages needs to be of adequate size. Also, the internal passages should be round in shape to accept the tubular elements that interconnect the heat transfer elements to the headers at both ends. When the internal surface area of the round internal passages increases, the volume of fluid also increases and the velocity of the fluid flow decreases, this increases the laminar flow of the heat transfer fluid. The laminar flow reduces heat transfer and contributes to an uneven surface temperature. This uneven surface temperature is undesirable.